密实截面组合梁的竖向抗剪强度Ⅱ:受负弯矩作用的组合梁

在负弯矩区段,虽存在严重的混凝土开裂,但组合梁的竖向抗剪承载力仍远大于钢梁腹板抗剪名义值.采用通用有限元程序ABAQUS 6.5,对密实截面组合梁负弯矩区的弯剪强度问题进行研究.分析结果表明,提出的有限元分析方法可以准确预测组合梁的弯剪强度,同时对组合梁的变形刚度也可以较准确地模拟.在此基础上,利用有限元方法,对剪力连接程度、混凝土强度、力比、混凝土翼板截面尺寸、剪跨长度等参数进行计算分析,回归得到组合梁负弯矩区截面考虑力比影响的竖向抗剪强度公式.研究发现,在负弯矩区段,组合梁竖向抗剪强度的提高,只来源于混凝土翼板的抗剪作用,组合作用的贡献可以忽略;采用建议的抗剪强度公式可以不考虑组合梁负弯矩区截面弯矩与剪力的相互影响.     

钢-混凝土组合梁在负弯矩作用下抗剪性能的试验研究

通过3根钢-混凝土组合梁在负弯矩作用下的试验,研究了其变形发展及破坏过程,得到了组合梁的跨中剪力-挠度曲线、交界面滑移曲线和沿截面高度分布的应变变化曲线,分析了剪切连接程度、截面尺寸、剪跨比、材料强度、钢筋配置等因素对组合梁承载力和延性的影响。对钢梁进行了塑性分析,得出在负弯矩作用下钢-混凝土组合梁抗剪承载力的提高不是由于钢梁腹板的硬化效应所致,而是由于混凝土翼板的贡献,并提出了考虑混凝土翼板影响的组合梁在负弯矩作用下抗剪承载力计算公式。将计算结果与实测结果进行了比较,二者吻合良好。     

钢-混凝土组合梁截面组合抗剪性能的试验研究

对4根密实截面钢-混凝土组合梁的组合抗剪性能进行了试验研究。试件全部采用简支,跨中两点对称单调静力加载,考虑抗剪连接程度及正负弯矩的影响。试验结果表明,组合梁负弯矩区的界面滑移规律与正弯矩区的不同,其大小对组合梁的抗剪承载能力影响较小。不论混凝土翼板是处于组合梁截面的受压区还是受拉区,其对组合梁截面的抗剪承载能力均有明显的贡献,目前规范仅计算钢梁腹板的抗剪作用偏于保守。按叠加法建立了计算组合梁抗剪承载能力的计算式,计算值与实测值吻合良好。     

腹板嵌入式外包U形钢-混凝土组合梁正弯矩区受弯性能研究

传统钢-混凝土组合梁需要焊接不同形式的抗剪连接件,为避免繁琐的焊接工序及焊接对钢材产生的不良影响,提出了腹板嵌入式外包U形钢-混凝土组合梁。在冷弯成型的U形钢腹板上部开槽,并嵌入到混凝土翼板,与板底横向钢筋共同组成带有混凝土榫连接件的腹板嵌入式外包U形钢-混凝土组合梁(WUCSB)。设计了8个WUSCB的正弯矩区受弯性能试验,考虑U形钢板厚度、连接件间距、混凝土翼缘板宽等参数的影响,分析组合梁的破坏模式,并基于荷载-挠度曲线和荷载-滑移曲线等试验结果对其刚度、承载力和延性等受力性能指标进行评价;建立了有限元模型,进行U形钢板厚度、混凝土翼缘板宽和梁底纵筋直径等3个参数的影响规律分析。试验结果表明：该组合梁满足完全抗剪连接,组合作用良好,U形钢可以达到全截面塑性,具有良好的整体受弯性能;增加U形钢板厚度和梁底纵筋直径可以提高组合梁的承载力;连接件间距、栓钉及箍筋对组合梁的承载力影响较小。基于试验结果和连接件的传力机理,给出了WUSCB抗剪连接度的计算方法;基于全截面塑性假定,给出了WUSCB受弯承载力设计方法,该承载力设计方法具有一定的安全储备。基于换算截面法,给出了受弯刚度计算方法,出...     

考虑剪力连接件刚度的钢-混凝土组合梁有限元分析

钢 -混凝土组合梁剪力连接程度是依据截面极限状态的抗弯强度定义的 ,即使是完全抗剪连接 ,组合梁的混凝土板与钢梁之间仍存在滑移。采用有限元分析 ,构造了混凝土板 -连接单元 -钢梁的组合梁有限元计算模型 ,推导了混凝土与钢梁界面有限元连接单元刚度系数 ,分析了不同剪力连接程度组合梁的受力与变形特性 ,研究了剪力连接程度对挠度和混凝土翼缘有效宽度的影响 ,并对照已有的试验数据和相关规范进行分析比较。     

钢-砼组合梁竖向抗剪承载力研究

在6根钢-火山渣砼简支组合梁和6根钢-火山渣砼连续组合梁试验的基础上，探讨影响组合梁竖向抗剪承载力的主要因素：混凝土翼板、名义剪跨比和力比等。试验与计算结果表明，在计算组合梁竖向抗剪承载力时，如果不考虑混凝土翼板的作用，计算结果将趋于保守，对于连续组合粱还应该考虑弯矩比的影响。     

侧锚钢-混凝土组合梁的试验研究

本文通过12根侧锚钢-混凝土组合梁试验分析,说明了侧锚组合梁的抗弯能力并不低于顶锚组合梁,当抗弯能力相当时,前者用钢量可减少约15%左右;具有完全剪力连接的侧锚组合粱的破坏弯矩可达到塑性铰弯矩。本试验还说明侧锚组合梁的刚度与连接件的间距有关,而且其破坏模式取决于连接件间距(或剪力连接程度);当采用加劲肋抗剪形式时,加劲肋能起到良好的抗剪作用。     

钢-砼组合梁竖向抗剪承载力研究

在6根钢-火山渣砼简支组合梁和6根钢-火山渣砼连续组合梁试验的基础上,探讨影响组合梁竖向抗剪承载力的主要因素:混凝土翼板、名义剪跨比和力比等。试验与计算结果表明,在计算组合梁竖向抗剪承载力时,如果不考虑混凝土翼板的作用,计算结果将趋于保守,对于连续组合梁还应该考虑弯矩比的影响。     

钢-混凝土组合梁界面滑移及变形性能的试验研究

对5根密实截面钢-混凝土组合梁的变形性能进行了试验研究。试件全部采用简支,跨中两点对称单调静力加载,考虑抗剪连接程度及栓钉布置形式的影响。得到各种情况下组合梁界面滑移分布曲线及弯矩-挠度曲线,分析其变形性能。试验结果及理论分析表明,现行钢结构规范规定的组合梁挠度计算公式对部分剪力连接组合梁来说偏于不安全,提出了相应的计算公式。     

钢-混凝土蜂窝组合梁抗剪性能分析

对腹板开孔后的蜂窝梁和考虑混凝土板组合作用下的蜂窝组合梁抗剪性能进行分析。以试验为基础,建立有限元模型,对不同开孔率、翼缘尺寸、混凝土板尺寸和连接程度下的蜂窝梁和蜂窝组合梁进行分析。结果表明:蜂窝梁翼缘宽度变化对抗剪贡献影响不大,翼缘厚度变化对其影响较大,翼缘厚度的抗剪贡献与开孔大小、形式有关;混凝土板和连接程度对蜂窝组合梁抗剪强度贡献不可忽略。给出了蜂窝梁、无连接蜂窝组合梁和有连接组合梁抗剪强度计算方法;通过分析不同剪跨比蜂窝组合梁的受力性能,给出弯-剪相关曲线公式;通过提高蜂窝组合梁孔洞竖向位置,可以提高其承载能力。     

窄梁和宽扁梁的设计分析

通过对模拟结构中采用宽扁梁和窄梁分别进行设计计算,比较其计算结果并分析造成宽扁梁弊端的主要原因,提出在结构设计中应尽量采用传统窄梁,避免设计宽扁梁。     

Distortion of thin-walled beams

First order Generalized Beam Theory (GBT) describes the behaviour of prismatic thin-walled structural members by using system of ordinary differential equations. Solution can lead to separation of the load components and then to subsequent combination of the stresses and deformations. Application of GBT to a steel, cold-formed, thin-walled cantilever beam with complex non-symmetrical open cross section is presented. Theoretical values are compared with experimental ones.     

Design of composite asymmetric cellular beams and beams with large web openings

The design of composite asymmetric cellular beams is not fully covered by existing guidance but is an area of important practical application. Asymmetry in the shape of the cross-section of cellular beams causes development of additional bending moments in the web-posts between closely placed openings. Furthermore, the development of local composite action influences the distribution of forces in the web-flange Tees. The design method presented in this paper takes account of high degrees of asymmetry in the cross-section and also the influence of elongated or rectangular openings.Web-post moments also influence buckling of the web-post between openings, which is accentuated by adjacent long openings. Simplified equations are presented for web-post buckling based on a compression field or ‘strut’ model, which is calibrated against the results of Finite Element Analyses (FEA). The FEA are also extended to cover the case of highly asymmetric sections and ring-stiffened openings. Closed solutions are presented that enable the designer to calculate the maximum shear force acting on the beam when its load resistance is limited by web-post bending or buckling.For long openings, high pull-out forces may exist in the shear connectors at the edge of the opening. When combined with possible second-order effects due to shear deflection across the opening, it is necessary to limit the magnitude of local composite action due to Vierendeel bending that can be considered in design.     

锈蚀钢筋混凝土梁抗弯承载力计算方法

基于锈蚀钢筋混凝土梁内钢筋与混凝土间黏结强度随锈蚀量的变化,对锈蚀梁的抗弯承载力进行了研究.当钢筋锈蚀量较小时,锈蚀梁内钢筋与混凝土间黏结强度随锈蚀量变化不大,锈蚀梁的力学性能同未锈蚀梁,可运用传统的梁理论计算锈蚀梁的抗弯承载力;但随着钢筋锈蚀量的增加,钢筋与混凝土间黏结强度发生退化,锈蚀梁的力学性能介于黏结完好梁与无...     

Simplified elasto-plastic analysis of composite beams and cellular beams to Eurocode 4

The elasto-plastic analysis of composite beams is important when considering the increase in bending resistance of the beam and the end slip between the steel and concrete at higher strains. This paper provides a simplified method of elasto-plastic analysis by considering equilibrium of the composite cross-section as a function of its strain profile. A parabolic-rectangular stress block for concrete is used in this model with a declining concrete strength at strains exceeding 0.0035. The bending resistance of the composite beam is expressed as a function of the bottom flange strain, and is compared to fully plastic design to EN 1994-1-1: Eurocode 4 and the AISC LRFD Code.The effect of various parameters on the development of the plastic bending resistance of composite beams is investigated, such as asymmetry of the section, the steel strength, the influence of propped or un-propped construction, strain hardening in the steel and reducing concrete strength at high strains, interface slip, and the effect of openings in the web of the beams. It was found that a moment of 95% of the plastic bending resistance of a composite beam (0.95M_p?) is reached at a flange strain of 2 to 4 × yield strain for propped beams and 5 to 10 × yield strain for un-propped beams. When strain hardening in the steel is included in the analysis, bottom flange strains at a moment of 0.95M_p? are reduced by up to 30% relative to the case without strain hardening.     

悬伸梁和双跨连续梁的整体稳定承载力试验研究

为了研究悬伸梁和双跨连续梁在集中荷载作用下的整体稳定性能,对两种单轴对称截面形式(上翼缘加强、下翼缘加强)、两种悬伸长度(1200mm、1600mm)共计5根悬伸梁,以及一种单轴对称截面形式(上翼缘加强)、三种相邻跨度之比(1∶0.48、1∶0.64、1∶1)共3根双跨连续梁进行了试验研究。在进行破坏试验前,对悬伸梁进行了三种荷载作用位置的弹性试验,对连续梁进行了三种加载比例的弹性试验,并利用Southwell法确定了临界荷载。试验研究结果表明:当最大弯矩出现在悬伸梁的简支跨且上翼缘受压时,上翼缘加强构件稳定承载力明显高于同尺寸的下翼缘加强构件;悬伸长度为1600mm的构件承载力明显高于悬伸长度为1200mm的构件承载力;荷载作用在简支梁段跨中时构件稳定承载力最低,荷载作用点离中间支座越近构件稳定承载力越高。双跨连续梁中,在等比例加载时,相邻跨度之比越大,构件稳定承载力越高。此外,对试验进行了有限元模拟,计算结果与试验结果吻合良好。     

运架梁一体机架梁施工技术

介绍了运架梁一体机的结构,详细阐述了900 t运架梁一体机架设双线整孔预制箱梁的施工技术以及箱梁架设应采取的安全技术措施,以促进运架梁一体机架梁技术在工程中的应用。     

Lateral-distortional buckling of tee-section beams

A fine element method that incorporates plate behaviour is developed for modelling the lateral-distortional buckling of tee-section beams. The method is shown to agree well with independent buckling results for tee-beams. Since relatively few elements are needed to obtain satisfactory convergence, the method is efficient computationally. The finite element analysis is used to study the elastic distortional buckling of tee-beams of practical geometry under moment gradient. The disparities found between the elastic flexural-torsional and distortional buckling moments are discussed.     

Distortional buckling of castellated beams

In previous studies of the structural behavior of castellated steel beams, different possible failure modes of these extensively used structural members have been identified and investigated. On the other hand, during the past 25 years or so, a proliferation of research work has been undertaken on the distortional buckling of steel members. Nonetheless, no studies are found in the literature on the distortional buckling of castellated beams. Accordingly, tests of six full-scale castellated beams are described, in which the experimental investigation of distortional buckling was the focus of interest. In addition to the test strengths, the accurate critical loads of the beams have been obtained using some extrapolation techniques, and ultimately a comparison has been made between the obtained test loads and some theoretical predictions.     

Buckling of laterally braced beams

This paper reports on thteral buckling tests of H-shaped beams unbraced or braced laterally by purlins or a sub-beam. These tested beams were subjected to uniform moment or moment gradient. The restraining effect of adjacent members, bracing effect of purlins or a sub-beam and effect of moment gradient on load carrying capacity and the post-lateral-buckling behaviour were investigated. Elastic-plastic analysis by means of the finite element method was performed to simulate the experimental behaviour. Analytical results were found to match well with experimental behaviour for the most part. Effective length factors that incorporate the effects of moment gradient, restraining, and bracing into design of H-shaped beams are discussed and proposed, based mainly on the analytical results.